# How does the Backward Chaining algorithm work in first order logic?

Can i get an explanation for the for each loop, because it doesn't make much sense to me. Particularly, what do STANDARDIZE-APART() and the second last line do?

which is FOL_BC_ASK(KB,[p1...,pn|REST(goals)],COMPOSE(@',@)) U ans

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Is this from Norvig & Russell? –  Ganesh Oct 12 '12 at 18:48
@Ganesh yes it is –  Ghost Oct 13 '12 at 5:02